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Simulations of Solar Cycles: cycles again!

An international team led by Prof. Paul Charbonneau, member of the Physics department at the Université de Montreal and member of the Centre de Recherche en Astrophysique du Québec, developed the most accurate simulations of the Solar cycles up to this the moment.

The effort, started more than five years ago at the Physics Department of the Université de Montréal, in collaboration with researchers from the National Centre for Atmospheric Research in Boulder, Colorado (USA), recently led to promising results. Using a novel numerical approach, the team led by Prof. Paul Charbonneau performed simulations of the Solar convection at a realistic physical regime[1]. The approach not only produces a well-organized magnetic field on large spatial scale, but it also presents regular polarity inversions. Both properties are observed in the evolution of the Solar magnetic field. The results were published in the prestigious specialized scientific journal "The Astrophysical Journal" on June 1st, 2010.

The Solar magnetic field is the main cause of the observed phenomena defining the Solar activity. The cyclic variation, observed for about 400 years in the evolution of Solar spots, modulates the energy output of the Sun. It also influences the frequency of all eruptive phenomena that affect the geospatial environment and the top-layers of our atmosphere. A physical understanding of the Solar influences on the Earth must therefore start with the appreciation of the dynamo process creating the magnetic field and of the polarity inversion in the magnetic Solar cycle.

Astrophysicists have attempted to model Solar cycles for more than 50 years. With the improvement of computers calculation power, the first simplified models were progressively replaced by precise turbulent magnetohydrodynamical simulations[2] of the outer layer of the Sun where the dynamo process exists. However, until recently, those simulations were not able to reproduce the magnetic field on large scales, or the polarity inversions.

For the first time, the simulations of Paul Charbonneau and his team help to elucidate, in a truly quantitative way, many questions for which only mere speculations had been suggested before. For example, it is now possible to quantify the impact of the cyclic magnetic field on the turbulent energy transport in the convective envelop of the Sun. This particular issue is very present in the debate on climate change because of the possible impact of the Solar activity.

The Solar physics research group at the Université de Montréal is funded by the Fonds Quebecois de la Recherche sur la Nature et les Technologies (FQRNT), the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canadian Research Chair program, the Canada Foundation for Innovation and the Canadian Space Agency. Most of the simulations were performed on the supercomputers of the Réseau Québecois de Calcul de Hautes Performances.

A snapshot of a numerical simulation of Solar convection, displaying convective cells on the surface (rising fluid in yellow, sinking fluid in red), and the intensity of the internal magnetic field (slice and inner shell, blue for a negative magnetic component and yellow for a positive component). A few lines of force are also traced and illustrate the complexity of the magnetic field produce in the simulation.

Source :
Paul Charbonneau, professeur titulaire,
Département de physique, Université de Montréal.
Groupe de recherche en physique solaire (GRPS)
CRAQ – Université de Montréal
Phone: 514-343-2300

Information :
Olivier Hernandez, Ph.D.,
CRAQ – Université de Montréal
Phone: 514-343-6111 ext 4681

[1] Convection is a mode of energy transfer involving a displacement of matter in a medium.

[2] Magnetohydrodynamic is the study of variations of magnetic fields in a gas, a liquid, a fluid or a plasma.

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